It's never a good thing when there is water, likely from the irrigation system, coming up from the base of a 40 foot poplar tree.
Often times the water will travel a fair distance and emerge at where there is least resistance. I had visions of a pretty big dig when I got nominated to do this repair.
Fortunately the broken pipe was directly below the water and with a shovel and an axe it turned out to be a pretty easy repair. But the question is: what came first, the pipe or the tree?